A variable air volume control box (VAV box) and a thermostat have been conventionally provided and generally used in order to control an air volume appropriate for a region to be air conditioned. Also, based on a nationally administered law on apartment house ventilation, many apartments have been equipped with ventilation equipment for forced ventilation.
In a configuration where an opening rate is controlled by driving a motor, the motor is provided in a flow passage or provided outside a diffuser or a duct. Such a structure has a problem in that for maintenance, disassembling and assembling are complicated to perform, and also, an additional maintenance hole has to be provided in a ceiling.